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In many areas of central Illinois, corn-after-corn yields were substantially below corn-after-soybean yields in 2010 and 2011. These yield drags, along with large increases in corn costs, have led some farmers to reevaluate corn-soybean cropping decisions. For land productivities that predominate in Illinois, corn-after-corn and continuous corn usually have higher budgeted returns than soybeans. However, more intense corn rotations reduce corn-after-soybeans acres, often some of the most profitable acres on a farm. Reduction in corn-after-soybean acres will impact returns in future years. This article examines the longer-run return impacts of corn-soybean rotations.

Corn-Soybean Budgets

Budgets for central Illinois are shown in Table 1 for high-productivity farmland. Budgets are given for corn after soybean, corn after corn, continuous corn, soybeans after corn and soybeans after two years corn.

Yields differ for the different budgets. Corn-after-soybean yield is 198 bu. Compared to corn after soybeans, corn after corn is bu. bushels less at 188 bu./acre and continuous corn is 18 bu. less at 180 bu./acre. Soybeans after corn has a 56-bu./acre yield. Soybeans after two years of corn have 3 bu. higher yield at 59 bu./acre. Differences in yields in these budgets reflect research conducted at the University of Illinois. Emerson Nafziger reported some of the corn yield research in a 2012 Corn & Soybean Classic Proceedings, “Fixing What Ails Continuous Corn” (Department of Crop Sciences, University of Illinois).

Non-land costs for corn after soybeans are $505/acre. Non-land costs for corn after corn and continuous corn are $15/acre higher at $520/acre, reflecting higher fertilizer and pesticide use. Costs in Table 1 do not include more tillage for corn after corn and continuous corn. If more tillage is used, costs would increase by $12-15/tillage pass.

Operator and land returns are:

$578 for corn after soybeans

$510 for corn after corn,

$467 for continuous corn

$390 for soybeans-after-corn

$425 for soybeans after two years corn

Not that all corn budgets have higher returns than soybean budgets. For the coming year, budgets suggest that returns are maximized by planting all corn.